Revert "Revert "Don't show HIDL_GENERATED_ with -Lc++-impl.""

Test: compiles

This reverts commit 119f521b1b03ce29c2e7f79c132483313e30a80a.

Change-Id: I16ff36c3c0c919056808e734dfbfc8cd9c8ca1d1
diff --git a/AST.h b/AST.h
index a4b4cda..12dfc89 100644
--- a/AST.h
+++ b/AST.h
@@ -153,7 +153,8 @@
             const FQName &package,
             const std::string &klass);
 
-    std::string makeHeaderGuard(const std::string &baseName) const;
+    std::string makeHeaderGuard(const std::string &baseName,
+                                bool indicateGenerated = true) const;
     void enterLeaveNamespace(Formatter &out, bool enter) const;
 
     static void generateCheckNonNull(Formatter &out, const std::string &nonNull);